The invention relates to a method for automatically detecting the installation position of brake force generating units of an electromagnetic motor vehicle brake system.
With respect to the background of the invention, it is noted that modern automobiles are being equipped with increasing numbers of electronic systems due to continuously rising requirements made in terms of active and passive safety, environmental compatibility and comfort. That applies particularly to driving characteristics which are being influenced to an increasing degree through the use of intelligent electronic control systems by intervening appropriately in the control of the engine and brakes. Examples thereof are anti-lock brake system, traction control system or electronic stability programs. The latter stabilize a vehicle which is tending to veer by selective braking interventions at the wheels.
However, such electronic interventions from the outside into the heretofore-known hydraulic braking system in order to implement the above-mentioned safety concepts make it necessary to use a large number of additional components such as valves, pumps and storage vessels. That makes such brake systems extremely complex and makes it difficult to provide control equipment therefor.
In order to overcome those problems, electromechanical brake systems have recently been developed in which the braking forces on the wheel are generated by using electromechanical transducers. Those transducers are activated through the use of a control system which senses pedal travel and/or activation pressure using suitable sensors and appropriately actuates the brakes. In that respect, the control unit of the brake system can integrate specific functions without difficulty, such as the aforementioned ABS, TCS, various brake boosting functions or the electronic stability program (ESP), into the electromechanical brake system.
In summary, such a xe2x80x9cbrake-by-wirexe2x80x9d system constitutes an external force brake system in which, when braking, the driver merely activates a brake pedal simulator having a movement which is in turn fed through sensors to a superordinate control unit, the xe2x80x9cbrake-by-wire managerxe2x80x9d.
Since the brake system is a vehicle system which is extremely relevant to safety, the safety concept, the reliability and the monitoring of that system are of central importance. In that regard, a monitoring computer generally monitors the brake-by-wire manager, the individual electromechanical transducers, the bus system connecting those components and the various sensors involved in the system. It is possible to detect, localize and diagnose fault states through the use of plausibility criteria and check routines within the control and monitoring program. Appropriate emergency functions can be activated as a function of the fault state in order to keep the brake system in a state which is as operationally reliable as possible.
A specific safety problem is presented by the correctly positioned installation of the brake force generating units which are respectively provided with a control device in the vehicle. The term xe2x80x9cinstallation positionxe2x80x9d is understood herein to be the relationship between the respective brake force generating unit and a quite specific wheel of the vehicle. Particularly in the context of electronic stability programs, all four wheels are in fact manipulated individually by braking interventions in order, for example, to prevent the vehicle from veering off. If a brake force generating unit which should in fact be positioned, for example, at the front left and appropriately actuated is installed at the front right, which is also caused by interchanging the wiring, with the same functional effect, xe2x80x9claterally invertedxe2x80x9d actuation of the individual brakes when an ESP intervention occurs would lead to further destabilization instead of to stabilization of the driving characteristics.
In practice, the above-mentioned problems have heretofore been accounted for merely by appropriate checking during installation and appropriate initialization of the control system.
It is accordingly an object of the invention to provide a method for automatically detecting the installation position of brake force generating units of an electromechanical motor vehicle brake system, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for automatically detecting the installation position of brake force generating units of an electromechanical motor vehicle brake system, which comprises sensing a steered direction of a motor vehicle during cornering. Wheel speeds occurring at each wheel of the motor vehicle during the cornering are sensed by using speed sensors assigned to respective brake force generating units. The wheel speed occurring for each wheel is compared with a setpoint position scheme of the wheel speeds that is representative of a direction of cornering. Actual positions of the brake force generating Units are determined based on the comparison.
The invention is based on the realization that during cornering significantly different wheel speeds which are dependent on the respective position of the wheel occur at the four wheels of a motor vehicle. In view of this it is therefore appropriate to sense the steering direction of the motor vehicle during cornering and check, on the basis of the knowledge of the steered direction, to what extent the wheel speeds are behaving xe2x80x9caccording to expectationsxe2x80x9d. If this is not the case, a faulty installation position must clearly be present.
Possible alternatives for sensing the steered direction of the vehicle are acceleration sensors or steering angle sensors. Such sensors are often installed in modern motor vehicles in any case because they are generally necessary for electronic stability programs and similar driving aids.
The verification method according to the invention is preferably carried out only up to a specified maximum steering angle and a specified maximum cornering speed in order to avoid incorrect detections due to limiting case effects. For example, it is possible for the setpoint position scheme of the wheel speeds to change at a very large steering angle. This is the case, for example, if the right-rear wheel describes a tighter curve than the left-front wheel on a left-hand curve.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for automatically detecting the installation position of brake force generating units of an electromagnetic motor vehicle brake system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.